Both hybrid models are advertised to return 47 mpg, but the owners say that number is inflated to seem more competitive among other midsize sedans, according to their court filing.

The complaint says car owners who have submitted estimates to a fuel-economy tracking website averaged 38.5 mpg, a 10-mpg difference that can cost an additional $1,800 in fuel costs over five years, Bloomberg reports.

“Ford’s fuel economy labels are generated in accordance with EPA procedures and protocols," Ford spokesman Todd Nissen said in an emailed statement to the wire service. He declined to comment on the lawsuit, citing that the company doesn't discuss pending legislation.